`completeopt` without `noselect` does not expand the auto-selected first entry

[dansalvato]

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Minimal reproducible full config

if has('vim_starting')
  set encoding=utf-8
endif
scriptencoding utf-8

if &compatible
  set nocompatible
endif

let s:plug_dir = expand('/tmp/plugged/vim-plug')
if !filereadable(s:plug_dir .. '/plug.vim')
  execute printf('!curl -fLo %s/autoload/plug.vim --create-dirs https://raw.githubusercontent.com/junegunn/vim-plug/master/plug.vim', s:plug_dir)
end

execute 'set runtimepath+=' . s:plug_dir
call plug#begin(s:plug_dir)
Plug 'hrsh7th/nvim-cmp'
Plug 'hrsh7th/cmp-buffer'
Plug 'hrsh7th/cmp-nvim-lsp'
Plug 'dcampos/nvim-snippy'
Plug 'dcampos/cmp-snippy'
Plug 'neovim/nvim-lspconfig'
call plug#end()
PlugInstall | quit

" Setup global configuration. More on configuration below.
lua << EOF
local cmp = require'cmp'

cmp.setup({
  snippet = {
    expand = function(args)
      require('snippy').expand_snippet(args.body)
    end,
  },
  completion = {
    autocomplete = false,
    completeopt = 'menu,menuone'
  },
  window = {
    completion = cmp.config.window.bordered({ border = 'single' }),
    documentation = cmp.config.window.bordered({ border = 'single' }),
  },
  mapping = cmp.mapping.preset.insert({
    ['<C-d>'] = cmp.mapping.scroll_docs(-4),
    ['<C-u>'] = cmp.mapping.scroll_docs(4),
    ['<C-e>'] = cmp.mapping.abort(),
    ['<C-y>'] = cmp.mapping.confirm({ select = true }),
  }),
  sources = cmp.config.sources({
    { name = 'nvim_lsp' },
    { name = 'snippy' }, -- For snippy users.
  }, {
    { name = 'buffer' },
  }),
  -- preselect = cmp.PreselectMode.Item,
})

cmp.setup({
  mapping = {
    ['<C-n>'] = function(_)
      if not cmp.visible() then
        cmp.complete()
      else
        cmp.select_next_item()
      end
    end,
  }
})
EOF

lua << EOF
local capabilities = require('cmp_nvim_lsp').update_capabilities(vim.lsp.protocol.make_client_capabilities())

require'lspconfig'.cssls.setup {
  capabilities = capabilities,
}
EOF

Description

I am trying to mimic the default Vim completion menu, in which pressing <C-n> will open the menu and select and expand the first entry. So, I set cmp's completeopt to menu,menuone. The first entry does indeed get selected on cmp.complete(), but it does not get expanded.

Steps to reproduce

1. Enter Insert mode and type a character.
2. Press <C-n> to open the completion menu (as mapped in my repro file).
3. Observe the first item gets selected, but it does not get expanded.
4. Further <C-n> and <C-p> inputs change the selection and do expand.
5. In a default or minimal nvim config, observe that pressing <C-n> to open the menu also selects and expands the first menu entry.

Expected behavior

The auto-selected first menu item should expand in the insert field.

Actual behavior

The first menu item gets selected, but the text does not get expanded until additional <C-n> or <C-p> inputs.

Additional context

No response

[hrsh7th]

Try use this.

      if not cmp.visible() then
        cmp.complete()
        vim.wait(500, function()
          return cmp.visible()
        end)
      end
      cmp.select_next_item()

Please don't use completeopt option.